net/9p/trans_xen.c

   1 /*
   2  * linux/fs/9p/trans_xen
   3  *
   4  * Xen transport layer.
   5  *
   6  * Copyright (C) 2017 by Stefano Stabellini <stefano@aporeto.com>
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License version 2
  10  * as published by the Free Software Foundation; or, when distributed
  11  * separately from the Linux kernel or incorporated into other
  12  * software packages, subject to the following license:
  13  *
  14  * Permission is hereby granted, free of charge, to any person obtaining a copy
  15  * of this source file (the "Software"), to deal in the Software without
  16  * restriction, including without limitation the rights to use, copy, modify,
  17  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
  18  * and to permit persons to whom the Software is furnished to do so, subject to
  19  * the following conditions:
  20  *
  21  * The above copyright notice and this permission notice shall be included in
  22  * all copies or substantial portions of the Software.
  23  *
  24  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  25  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  26  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  27  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  28  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  29  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  30  * IN THE SOFTWARE.
  31  */
  32
  33 #include <xen/events.h>
  34 #include <xen/grant_table.h>
  35 #include <xen/xen.h>
  36 #include <xen/xenbus.h>
  37 #include <xen/interface/io/9pfs.h>
  38
  39 #include <linux/module.h>
  40 #include <linux/spinlock.h>
  41 #include <net/9p/9p.h>
  42 #include <net/9p/client.h>
  43 #include <net/9p/transport.h>
  44
  45 #define XEN_9PFS_NUM_RINGS 2
  46 #define XEN_9PFS_RING_ORDER 6
  47 #define XEN_9PFS_RING_SIZE  XEN_FLEX_RING_SIZE(XEN_9PFS_RING_ORDER)
  48
  49 struct xen_9pfs_header {
  50         uint32_t size;
  51         uint8_t id;
  52         uint16_t tag;
  53
  54         /* uint8_t sdata[]; */
  55 } __attribute__((packed));
  56
  57 /* One per ring, more than one per 9pfs share */
  58 struct xen_9pfs_dataring {
  59         struct xen_9pfs_front_priv *priv;
  60
  61         struct xen_9pfs_data_intf *intf;
  62         grant_ref_t ref;
  63         int evtchn;
  64         int irq;
  65         /* protect a ring from concurrent accesses */
  66         spinlock_t lock;
  67
  68         struct xen_9pfs_data data;
  69         wait_queue_head_t wq;
  70         struct work_struct work;
  71 };
  72
  73 /* One per 9pfs share */
  74 struct xen_9pfs_front_priv {
  75         struct list_head list;
  76         struct xenbus_device *dev;
  77         char *tag;
  78         struct p9_client *client;
  79
  80         int num_rings;
  81         struct xen_9pfs_dataring *rings;
  82 };
  83
  84 static LIST_HEAD(xen_9pfs_devs);
  85 static DEFINE_RWLOCK(xen_9pfs_lock);
  86
  87 /* We don't currently allow canceling of requests */
  88 static int p9_xen_cancel(struct p9_client *client, struct p9_req_t *req)
  89 {
  90         return 1;
  91 }
  92
  93 static int p9_xen_create(struct p9_client *client, const char *addr, char *args)
  94 {
  95         struct xen_9pfs_front_priv *priv;
  96
  97         read_lock(&xen_9pfs_lock);
  98         list_for_each_entry(priv, &xen_9pfs_devs, list) {
  99                 if (!strcmp(priv->tag, addr)) {
 100                         priv->client = client;
 101                         read_unlock(&xen_9pfs_lock);
 102                         return 0;
 103                 }
 104         }
 105         read_unlock(&xen_9pfs_lock);
 106         return -EINVAL;
 107 }
 108
 109 static void p9_xen_close(struct p9_client *client)
 110 {
 111         struct xen_9pfs_front_priv *priv;
 112
 113         read_lock(&xen_9pfs_lock);
 114         list_for_each_entry(priv, &xen_9pfs_devs, list) {
 115                 if (priv->client == client) {
 116                         priv->client = NULL;
 117                         read_unlock(&xen_9pfs_lock);
 118                         return;
 119                 }
 120         }
 121         read_unlock(&xen_9pfs_lock);
 122 }
 123
 124 static bool p9_xen_write_todo(struct xen_9pfs_dataring *ring, RING_IDX size)
 125 {
 126         RING_IDX cons, prod;
 127
 128         cons = ring->intf->out_cons;
 129         prod = ring->intf->out_prod;
 130         virt_mb();
 131
 132         return XEN_9PFS_RING_SIZE -
 133                 xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE) >= size;
 134 }
 135
 136 static int p9_xen_request(struct p9_client *client, struct p9_req_t *p9_req)
 137 {
 138         struct xen_9pfs_front_priv *priv = NULL;
 139         RING_IDX cons, prod, masked_cons, masked_prod;
 140         unsigned long flags;
 141         u32 size = p9_req->tc->size;
 142         struct xen_9pfs_dataring *ring;
 143         int num;
 144
 145         read_lock(&xen_9pfs_lock);
 146         list_for_each_entry(priv, &xen_9pfs_devs, list) {
 147                 if (priv->client == client)
 148                         break;
 149         }
 150         read_unlock(&xen_9pfs_lock);
 151         if (!priv || priv->client != client)
 152                 return -EINVAL;
 153
 154         num = p9_req->tc->tag % priv->num_rings;
 155         ring = &priv->rings[num];
 156
 157 again:
 158         while (wait_event_killable(ring->wq,
 159                                    p9_xen_write_todo(ring, size)) != 0)
 160                 ;
 161
 162         spin_lock_irqsave(&ring->lock, flags);
 163         cons = ring->intf->out_cons;
 164         prod = ring->intf->out_prod;
 165         virt_mb();
 166
 167         if (XEN_9PFS_RING_SIZE - xen_9pfs_queued(prod, cons,
 168                                                  XEN_9PFS_RING_SIZE) < size) {
 169                 spin_unlock_irqrestore(&ring->lock, flags);
 170                 goto again;
 171         }
 172
 173         masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE);
 174         masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE);
 175
 176         xen_9pfs_write_packet(ring->data.out, p9_req->tc->sdata, size,
 177                               &masked_prod, masked_cons, XEN_9PFS_RING_SIZE);
 178
 179         p9_req->status = REQ_STATUS_SENT;
 180         virt_wmb();                     /* write ring before updating pointer */
 181         prod += size;
 182         ring->intf->out_prod = prod;
 183         spin_unlock_irqrestore(&ring->lock, flags);
 184         notify_remote_via_irq(ring->irq);
 185
 186         return 0;
 187 }
 188
 189 static void p9_xen_response(struct work_struct *work)
 190 {
 191         struct xen_9pfs_front_priv *priv;
 192         struct xen_9pfs_dataring *ring;
 193         RING_IDX cons, prod, masked_cons, masked_prod;
 194         struct xen_9pfs_header h;
 195         struct p9_req_t *req;
 196         int status;
 197
 198         ring = container_of(work, struct xen_9pfs_dataring, work);
 199         priv = ring->priv;
 200
 201         while (1) {
 202                 cons = ring->intf->in_cons;
 203                 prod = ring->intf->in_prod;
 204                 virt_rmb();
 205
 206                 if (xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE) <
 207                     sizeof(h)) {
 208                         notify_remote_via_irq(ring->irq);
 209                         return;
 210                 }
 211
 212                 masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE);
 213                 masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE);
 214
 215                 /* First, read just the header */
 216                 xen_9pfs_read_packet(&h, ring->data.in, sizeof(h),
 217                                      masked_prod, &masked_cons,
 218                                      XEN_9PFS_RING_SIZE);
 219
 220                 req = p9_tag_lookup(priv->client, h.tag);
 221                 if (!req || req->status != REQ_STATUS_SENT) {
 222                         dev_warn(&priv->dev->dev, "Wrong req tag=%x\n", h.tag);
 223                         cons += h.size;
 224                         virt_mb();
 225                         ring->intf->in_cons = cons;
 226                         continue;
 227                 }
 228
 229                 memcpy(req->rc, &h, sizeof(h));
 230                 req->rc->offset = 0;
 231
 232                 masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE);
 233                 /* Then, read the whole packet (including the header) */
 234                 xen_9pfs_read_packet(req->rc->sdata, ring->data.in, h.size,
 235                                      masked_prod, &masked_cons,
 236                                      XEN_9PFS_RING_SIZE);
 237
 238                 virt_mb();
 239                 cons += h.size;
 240                 ring->intf->in_cons = cons;
 241
 242                 status = (req->status != REQ_STATUS_ERROR) ?
 243                         REQ_STATUS_RCVD : REQ_STATUS_ERROR;
 244
 245                 p9_client_cb(priv->client, req, status);
 246         }
 247 }
 248
 249 static irqreturn_t xen_9pfs_front_event_handler(int irq, void *r)
 250 {
 251         struct xen_9pfs_dataring *ring = r;
 252
 253         if (!ring || !ring->priv->client) {
 254                 /* ignore spurious interrupt */
 255                 return IRQ_HANDLED;
 256         }
 257
 258         wake_up_interruptible(&ring->wq);
 259         schedule_work(&ring->work);
 260
 261         return IRQ_HANDLED;
 262 }
 263
 264 static struct p9_trans_module p9_xen_trans = {
 265         .name = "xen",
 266         .maxsize = 1 << (XEN_9PFS_RING_ORDER + XEN_PAGE_SHIFT),
 267         .def = 1,
 268         .create = p9_xen_create,
 269         .close = p9_xen_close,
 270         .request = p9_xen_request,
 271         .cancel = p9_xen_cancel,
 272         .owner = THIS_MODULE,
 273 };
 274
 275 static const struct xenbus_device_id xen_9pfs_front_ids[] = {
 276         { "9pfs" },
 277         { "" }
 278 };
 279
 280 static void xen_9pfs_front_free(struct xen_9pfs_front_priv *priv)
 281 {
 282         int i, j;
 283
 284         write_lock(&xen_9pfs_lock);
 285         list_del(&priv->list);
 286         write_unlock(&xen_9pfs_lock);
 287
 288         for (i = 0; i < priv->num_rings; i++) {
 289                 if (!priv->rings[i].intf)
 290                         break;
 291                 if (priv->rings[i].irq > 0)
 292                         unbind_from_irqhandler(priv->rings[i].irq, priv->dev);
 293                 if (priv->rings[i].data.in) {
 294                         for (j = 0; j < (1 << XEN_9PFS_RING_ORDER); j++) {
 295                                 grant_ref_t ref;
 296
 297                                 ref = priv->rings[i].intf->ref[j];
 298                                 gnttab_end_foreign_access(ref, 0, 0);
 299                         }
 300                         free_pages((unsigned long)priv->rings[i].data.in,
 301                                    XEN_9PFS_RING_ORDER -
 302                                    (PAGE_SHIFT - XEN_PAGE_SHIFT));
 303                 }
 304                 gnttab_end_foreign_access(priv->rings[i].ref, 0, 0);
 305                 free_page((unsigned long)priv->rings[i].intf);
 306         }
 307         kfree(priv->rings);
 308         kfree(priv->tag);
 309         kfree(priv);
 310 }
 311
 312 static int xen_9pfs_front_remove(struct xenbus_device *dev)
 313 {
 314         struct xen_9pfs_front_priv *priv = dev_get_drvdata(&dev->dev);
 315
 316         dev_set_drvdata(&dev->dev, NULL);
 317         xen_9pfs_front_free(priv);
 318         return 0;
 319 }
 320
 321 static int xen_9pfs_front_alloc_dataring(struct xenbus_device *dev,
 322                                          struct xen_9pfs_dataring *ring)
 323 {
 324         int i = 0;
 325         int ret = -ENOMEM;
 326         void *bytes = NULL;
 327
 328         init_waitqueue_head(&ring->wq);
 329         spin_lock_init(&ring->lock);
 330         INIT_WORK(&ring->work, p9_xen_response);
 331
 332         ring->intf = (struct xen_9pfs_data_intf *)get_zeroed_page(GFP_KERNEL);
 333         if (!ring->intf)
 334                 return ret;
 335         ret = gnttab_grant_foreign_access(dev->otherend_id,
 336                                           virt_to_gfn(ring->intf), 0);
 337         if (ret < 0)
 338                 goto out;
 339         ring->ref = ret;
 340         bytes = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
 341                         XEN_9PFS_RING_ORDER - (PAGE_SHIFT - XEN_PAGE_SHIFT));
 342         if (!bytes) {
 343                 ret = -ENOMEM;
 344                 goto out;
 345         }
 346         for (; i < (1 << XEN_9PFS_RING_ORDER); i++) {
 347                 ret = gnttab_grant_foreign_access(
 348                                 dev->otherend_id, virt_to_gfn(bytes) + i, 0);
 349                 if (ret < 0)
 350                         goto out;
 351                 ring->intf->ref[i] = ret;
 352         }
 353         ring->intf->ring_order = XEN_9PFS_RING_ORDER;
 354         ring->data.in = bytes;
 355         ring->data.out = bytes + XEN_9PFS_RING_SIZE;
 356
 357         ret = xenbus_alloc_evtchn(dev, &ring->evtchn);
 358         if (ret)
 359                 goto out;
 360         ring->irq = bind_evtchn_to_irqhandler(ring->evtchn,
 361                                               xen_9pfs_front_event_handler,
 362                                               0, "xen_9pfs-frontend", ring);
 363         if (ring->irq >= 0)
 364                 return 0;
 365
 366         xenbus_free_evtchn(dev, ring->evtchn);
 367         ret = ring->irq;
 368 out:
 369         if (bytes) {
 370                 for (i--; i >= 0; i--)
 371                         gnttab_end_foreign_access(ring->intf->ref[i], 0, 0);
 372                 free_pages((unsigned long)bytes,
 373                            XEN_9PFS_RING_ORDER -
 374                            (PAGE_SHIFT - XEN_PAGE_SHIFT));
 375         }
 376         gnttab_end_foreign_access(ring->ref, 0, 0);
 377         free_page((unsigned long)ring->intf);
 378         return ret;
 379 }
 380
 381 static int xen_9pfs_front_probe(struct xenbus_device *dev,
 382                                 const struct xenbus_device_id *id)
 383 {
 384         int ret, i;
 385         struct xenbus_transaction xbt;
 386         struct xen_9pfs_front_priv *priv = NULL;
 387         char *versions;
 388         unsigned int max_rings, max_ring_order, len = 0;
 389
 390         versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
 391         if (!len)
 392                 return -EINVAL;
 393         if (strcmp(versions, "1")) {
 394                 kfree(versions);
 395                 return -EINVAL;
 396         }
 397         kfree(versions);
 398         max_rings = xenbus_read_unsigned(dev->otherend, "max-rings", 0);
 399         if (max_rings < XEN_9PFS_NUM_RINGS)
 400                 return -EINVAL;
 401         max_ring_order = xenbus_read_unsigned(dev->otherend,
 402                                               "max-ring-page-order", 0);
 403         if (max_ring_order < XEN_9PFS_RING_ORDER)
 404                 return -EINVAL;
 405
 406         priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 407         if (!priv)
 408                 return -ENOMEM;
 409
 410         priv->dev = dev;
 411         priv->num_rings = XEN_9PFS_NUM_RINGS;
 412         priv->rings = kcalloc(priv->num_rings, sizeof(*priv->rings),
 413                               GFP_KERNEL);
 414         if (!priv->rings) {
 415                 kfree(priv);
 416                 return -ENOMEM;
 417         }
 418
 419         for (i = 0; i < priv->num_rings; i++) {
 420                 priv->rings[i].priv = priv;
 421                 ret = xen_9pfs_front_alloc_dataring(dev, &priv->rings[i]);
 422                 if (ret < 0)
 423                         goto error;
 424         }
 425
 426  again:
 427         ret = xenbus_transaction_start(&xbt);
 428         if (ret) {
 429                 xenbus_dev_fatal(dev, ret, "starting transaction");
 430                 goto error;
 431         }
 432         ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
 433         if (ret)
 434                 goto error_xenbus;
 435         ret = xenbus_printf(xbt, dev->nodename, "num-rings", "%u",
 436                             priv->num_rings);
 437         if (ret)
 438                 goto error_xenbus;
 439         for (i = 0; i < priv->num_rings; i++) {
 440                 char str[16];
 441
 442                 BUILD_BUG_ON(XEN_9PFS_NUM_RINGS > 9);
 443                 sprintf(str, "ring-ref%u", i);
 444                 ret = xenbus_printf(xbt, dev->nodename, str, "%d",
 445                                     priv->rings[i].ref);
 446                 if (ret)
 447                         goto error_xenbus;
 448
 449                 sprintf(str, "event-channel-%u", i);
 450                 ret = xenbus_printf(xbt, dev->nodename, str, "%u",
 451                                     priv->rings[i].evtchn);
 452                 if (ret)
 453                         goto error_xenbus;
 454         }
 455         priv->tag = xenbus_read(xbt, dev->nodename, "tag", NULL);
 456         if (IS_ERR(priv->tag)) {
 457                 ret = PTR_ERR(priv->tag);
 458                 goto error_xenbus;
 459         }
 460         ret = xenbus_transaction_end(xbt, 0);
 461         if (ret) {
 462                 if (ret == -EAGAIN)
 463                         goto again;
 464                 xenbus_dev_fatal(dev, ret, "completing transaction");
 465                 goto error;
 466         }
 467
 468         write_lock(&xen_9pfs_lock);
 469         list_add_tail(&priv->list, &xen_9pfs_devs);
 470         write_unlock(&xen_9pfs_lock);
 471         dev_set_drvdata(&dev->dev, priv);
 472         xenbus_switch_state(dev, XenbusStateInitialised);
 473
 474         return 0;
 475
 476  error_xenbus:
 477         xenbus_transaction_end(xbt, 1);
 478         xenbus_dev_fatal(dev, ret, "writing xenstore");
 479  error:
 480         dev_set_drvdata(&dev->dev, NULL);
 481         xen_9pfs_front_free(priv);
 482         return ret;
 483 }
 484
 485 static int xen_9pfs_front_resume(struct xenbus_device *dev)
 486 {
 487         dev_warn(&dev->dev, "suspend/resume unsupported\n");
 488         return 0;
 489 }
 490
 491 static void xen_9pfs_front_changed(struct xenbus_device *dev,
 492                                    enum xenbus_state backend_state)
 493 {
 494         switch (backend_state) {
 495         case XenbusStateReconfiguring:
 496         case XenbusStateReconfigured:
 497         case XenbusStateInitialising:
 498         case XenbusStateInitialised:
 499         case XenbusStateUnknown:
 500                 break;
 501
 502         case XenbusStateInitWait:
 503                 break;
 504
 505         case XenbusStateConnected:
 506                 xenbus_switch_state(dev, XenbusStateConnected);
 507                 break;
 508
 509         case XenbusStateClosed:
 510                 if (dev->state == XenbusStateClosed)
 511                         break;
 512                 /* Missed the backend's CLOSING state -- fallthrough */
 513         case XenbusStateClosing:
 514                 xenbus_frontend_closed(dev);
 515                 break;
 516         }
 517 }
 518
 519 static struct xenbus_driver xen_9pfs_front_driver = {
 520         .ids = xen_9pfs_front_ids,
 521         .probe = xen_9pfs_front_probe,
 522         .remove = xen_9pfs_front_remove,
 523         .resume = xen_9pfs_front_resume,
 524         .otherend_changed = xen_9pfs_front_changed,
 525 };
 526
 527 static int p9_trans_xen_init(void)
 528 {
 529         if (!xen_domain())
 530                 return -ENODEV;
 531
 532         pr_info("Initialising Xen transport for 9pfs\n");
 533
 534         v9fs_register_trans(&p9_xen_trans);
 535         return xenbus_register_frontend(&xen_9pfs_front_driver);
 536 }
 537 module_init(p9_trans_xen_init);
 538
 539 static void p9_trans_xen_exit(void)
 540 {
 541         v9fs_unregister_trans(&p9_xen_trans);
 542         return xenbus_unregister_driver(&xen_9pfs_front_driver);
 543 }
 544 module_exit(p9_trans_xen_exit);
 545
 546 MODULE_AUTHOR("Stefano Stabellini <stefano@aporeto.com>");
 547 MODULE_DESCRIPTION("Xen Transport for 9P");
 548 MODULE_LICENSE("GPL");